Pressure sensitive record material



Patented Apr. 24, 1951 PRESSURE SENSITIVE RECORD MATERIAL Barrett K. Green and Robert W. Sandberg, Dayton, Ohio, assignors to The National Cash Register Company, Dayton, Ohio, a corporation of Maryland No Drawing. Original application July 13, 1948,

Serial No. 38,547. Divided and this application September 15, 1950, Serial No. 185,153

2 Claims.

record material and more particularly pertains to such material having minute particles of two kinds of substances which are color-reactive on contact, one of the substances being in liquid form and the other being in solid form, the particles of the two substances being arranged in proximity in profuse numbers but insulated from contact by material rupturable when pressure is applied, which pressure acts to bring the two kinds of substances together at the points of ruptime to produce a distinctively-colored localized mark.

This is a division of United States patent application No. 38,547, filed July 13, 1948, by applicants herein.

The record material of this invention, although adapted for response to stylus pressures, is particularly adapted for response to pressures applied in impact printing operations, such as by the striking or pressing of type thereagainst, and in that respect is an improvement over the record material of Barrett K. Greens United States Patent No. 2,505,470, for Pressure-Sensitive Record Material, which was granted April 25, 1950.

- The record material disclosed therein required the bringing together, by pressure, of two kinds of solid particles embedded in a rupturable solid insulating film. The low mobility of such solid particles rendered that record material more sensitive to pressures caused by drawing a stylus thereover than to pressures derived from the impact of type. This novel record material also is an improvement over that record material disclosed in United States Letters Patent No. 2,299,693, patented on October 20, 1942, on the application of Barrett K. Green. That patent discloses pressure-sensitive record material especially adapted for impact work, such material including a rupturable insulating medium in which are interspersed liquid droplets of two kinds which react on contact to form color. The liquid droplets included solid color-forming materials dissolved in an ionizing medium, glycerine, which reacted to produce color on contact by interchange of ions. Any liquid ionizing medium available for use in such a system is hygroscopic, making the record material unduly sensitive to moisture.

The present invention provides a record material with exceptional response to impact presreactant substance is a non-ionizing inert oily type of material which is non-hygroscopicand is used solely to dissolve the active ingredient and to obtain easier release and greater mobility of the droplets when the supporting film is rup-.. tured. Because of the mobility of the released liquid droplets at points of rupture of the insulating medium, the new record material is highly sensitive both to drawing and to impact pressures, yet it is resistant to destructive influ-' ences encountered in ordinary environment and normal handling operations. Thus, the new record material combines the best characteristics of known pressure-responsive record materials by providing a novel liquid-solid reactant structure.

The principal object of the invention is to provide a pressure-sensitive .record material on which a mark of distinctive color may be pro-- duced by the mere application of localized pres-' sure, said material including color-forming substances of two kinds, one being solid and the other being liquid, the two substances normally being held insulated from reaction contact by a rupturable insulating medium until marking pressures rupture the insulating medium at points of pressure to bring about local contact of the two substances to produce a mark.

Another object of the invention is to provide a record material in which one of the color reactant substances is dissolved in a non-ionizing oily liquid which may be dispersed as droplets in a rupturable solid insulating film so as to be readily available and mobile locally to make contact with the other solid reactant material when released by rupture of the film. Another object of the invention is to provide such a record material which is highly sensitive to impact pressures, such as those met with in typewriter or letter press work, and for this effect the two color reactants are arranged in separate overlying layers on a web, so that marking pressures vertically applied to the said layers will cause penetration of the color reactant substances of one layer into that of the otherlayer. Further objects, and objects relating to details and economies of production, will definitely appear from the detailed description to follow. The objects of this invention have been attained by the several embodiments thereof described in detail in the following specification. The invention isclearly defined and pointed out in the appended claims.

Inthe preferred form of this invention, the

liquid droplets of color reactant are dispersed in a film-forming substance which is applied as a coating to a paper web and dried thereon, leav-' ingthe liquid droplets entrapped therein. The

solid color reactant particles, acting as adsorbents, are likewise dispersed in a film-form ing substancewhich is appliedas a second over-'- 3 lying coating. Both films are rupturable to force the reactant substances together.

or the: reactant; materials employed, th liquid droplets contain an organic substance which is an electron donor aromatic compound having av double bond system which is converted to a more highly polarized conjugated form upon: takingpart in an electron donor-acceptor adsorption chemical reaction, givin it a distinctive. color, and the solid particles are. of an inorganic substance which is an acid relative to the organic substance so as to be an electron acceptor when in adsorption contact therewith. The soli'd'material is in fine particle form in order to furnish a large reactant surface per unitarea of the record material, which enhances the depth of color produced in the record material.

The. film-forming substances are derivedfrom hydrophilic colloid materials that form pressure.- rupturable films..

The. adsorbate substance may include one or more. kinds of reactant'such. as crystal violet lact'one}, which is 323 bis(p-dimethylaminopheny1)- 6diinethylamino. phthal'ide, and tetrachloromalachite green lactone mixecttogether anddissolved in the oily liquid.

The web used as. a. support may be paper or other material suitableas a record. base. For instance, either cardboard, glass, metal, or wood may be usedv if. desired. The total thickness of the pressure-sensitive film need. be no greater than fi1om..00ll to. .002. of. an inch, so that it may be supported on. very thin paper stock. By placing a number of such thin-coated paper sheets irrsuperimposed relation in. a typewriter, a numher of printed copies of typewritten materialmay be made without the use of a typewriter ink ribbon or carbon. manifold paper, asis now the common. practice.

As it is difficult, if not impossible, to show the exact structure. of this coating by use of a drawing, none accompanies this specification.

In. the. following examples, there will be described. embodiments of this invention by which the objects of the invention have been successfully attained.

Example 1.--The following embodiment of this invention constitutes the best mode of applying the principles thereof as contemplated up to the present time. and may be considered the preferred embodiment. It comprises a base web of paper or the like, on one surfaceof which two coatings are applied, the first, or under, coating bein an insulating film in which are entrapped a profuse number of liquid droplets in which a color reactantsubstance is dissolved. These droplets are, on the average, of the: order of from 1 to microns in diameter and are spaced apart, on the average, a distance of the order of micron. The preferred thickness of this first coating, when dry, is of the order of .001 of an inch.

The first coating is made by dissolving one part by weight of animal gelatin, having an isoelectric point of pH 8 and a jelly strength of 275 grams as measured by the Bloom gelometer, with three parts by weight of water heated to 150 degrees Fahrenheit.

Into four parts by weight of the gelatin solutionthere is dispersed, or emulsified, three parts by weight of a solution of crystal violet lactone in chlorinated diphenyl.

This solution of crystal violet lactone, which is 3,3 bispdimethylaminophenyl) 6 dimethylaminophthalide, in chlorinated diphenyl is made by dissolving three parts. by weight of the crystal violet lactone in ninety-seven parts by weight of chlorinated diphenyl. which has. a chlorine content averaging 48% by weight. This chlorinated diphenyl solution is heated to the temperature of the gelatin solution before it is added thereto and emulsified.

The emulsion. is, applied while sill hot or, if allowed to 0001,, after being reheated to 150 degrees Fahrenheit and is dried either under normal. atmospheric conditions or by artificial means such as a hotair: blast or on a heated drying drum such as those commonly used in papercoati'ng machines. It is considered that drying under'normal atmospheric environment gives a somewhat better water resistance to the dried filmor." coating in which the chlorinated diphenyl solution droplets are entrapped.

The dried. undercoating is next, treated to drive thedroplets out. of the top surface layer and into the interiorv of the film so as, in effect, to form an impermeable. surface. skin thereon. This is accompl-ished by wetting the surface with water at room temp-eraturethat is, from 70 to 80 degrees Fahrenheit-which water has had added thereto 1% by weight of formaldehyde and 0.1% by weight of a wettingv agent such as dioctyl ester of sodium sulfosuccinate. The wetting should be allowed topersist for several minutes, and thereafter the film is dried in a low-humidity atmos phere. The surface wetting may be accomplished by floating the. coated paper on the water, coated face down, or by carrying it on a partially sub.- merged drum with the coated surface facing outwardly. The formaldehyde may be omitted, if desired.

The second coating, or overcoating, is then ap plied to the dried undercoating. In making the second coating, 20%, by weight, of paper-coating starch in water is cooked at 200 degrees Fahren heit for- 15 minutes and cooled to room tempera-- ture. Separately, 1 part by weight of halloysite is dispersed in three parts by weight of water by use of a ball mill or equivalent. Four parts, by weight, of the halloysite dispersion is mixed with one part, by weight, of the starch solution. The resultant mixture is applied, at room temperatu-re, as an overcoating to the prepared paper having the gelatine coating dried thereon. This starchhalloysite overcoating is applied in any convenient manner, as by a paper-coating machine. This overcoating, when dry, should have a thickness of the order of .0005 of an inch.

The thickness of the undercoating and the overcoating may be varied somewhat without inter fering greatly with the sensitivity of the material, such variation range being of the order of 25% in: either direction.

The record material, when finished, has a substantially white appearance and produces a dark blue mark which sharply defines the area of pressure or impact.

The impact of a marking instrument on the surface of this record material locally releases the oily droplets from the gelatine film and forces them into contact with the overlying halloysite particles. The needle-like crystal aggregate structure of halloysite prevents any substantial 8. The compound crystal violet lactone has the structure oHmN- more and the process of making it is described in United States Letters Patent No. 2,417,897, issued March 25, 1947, on the application of Clyde S. Adams filed June 16, 1945, which patent was reissued on August 17, 1948, under N0. Re. 23,024.

Example 2.-Another embodiment of the invention is the use of malachite green lactone; that is to say, 3,3 bis(p-dimethylaminophenyl) phthalide, having the structure in place of the crystal violet lactone of Example 1 and in the same amount. This gives a substantially white record material producing a green mark when pressure is applied.

Example 4.-Another embodiment of the invention is the use of 3,3 bis(p-diethylaminophenyl)-fi-dimethylamino phthalide, having the structure in place of the crystal violet lactone of Example 1 and in the same amount. 7 This gives a substantially white record material producing a blue mark when pressure is applied.

The adsorbent material should be accessible to the liquid droplets containing the color reactant material to be adsorbed thereon, and the action of the coating binder tends to mask the exterior surface available on such adsorbent particles. Halloysite seems to be of such structure as has available interior adsorbent surfaces and therefore is eminently suitable to act as the adsorbent material of the system.

The methods and processes of making the pressure-sensitive record material as disclosed herein are disclosed and claimed in a co-pending application of Barrett K. Green and Robert W. Sandberg, Serial No. 38,548, filed July 13, 1948.

It is understood that the pressure-sensitive record material described herein is susceptible of considerable variations without departing from the spirit f the invention.

What is claimed is:

l. Pressure-sensitive record material including the combination of color-forming substances of two kinds, one kind being solid and the other kind being liquid, said liquid kind being held insulated from contact with the solid kind by being profusely dispersed in minute droplets in a solid rupturable film on the exterior of which is deposited a film bearing particles of the solid kind, the application of localized pressure to the I record material rupturing the film at points of application and there bringing the color-forming substances together, whereby a distinctivelycolored mark is produced by mere application of localized pressure, and said solid color-forming substance being particles of halloysite, and said liquid color-forming substance being an organic electron donor aromatic compound having a double bond system which is converted to a more highly polarized conjugated form upon taking part in an electron donor-acceptor adsorption chemical reaction, giving it a distinctive color.

2. Pressure-forming record material including the combination of a supporting web; a continuous rupturable solid insulatin film applied thereto, said film containing dispersed therethrough a profusion of minute liquid colorforming inclusions; and a coating on the outer surface of the insulating film, said coating containing a profuse number of solid color-forming particles which, when brought into contact with the liquid inclusions by application of localized pressure to the record material which ruptures the insulating film and coating, react with said liquid inclusions to form a distinctively-colored mark at said points of localized pressure, and said solid color-forming particles being halloysite, and said liquid color-forming substance being an organic electron donor aromatic compound having a double bond system which is converted to a more'highly polarized conjugated form upon taking part in an electron donoracceptor adsorption chemical reaction, giving it a distinctive color.

BARRETT K. GREEN. ROBERT W. SANDBERG.

No references cited. 

